Dependence of diffuse photosynthetically active solar irradiance on total optical depth

Hi Ku Cho, Myeong J. Jeong, Jhoon Kim, Young J. Kim

Research output: Contribution to journalArticle

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Abstract

Photosynthetically active solar irradiance (PAR, 400-700 nm) data measured with a rotating shadowband radiometer at Yonsei University, Seoul (37.57°N, 126.97°E) from 1996 through 1997 have been analyzed to investigate statistical features in components of the horizontal PAR and the dependence of the diffuse PAR on total optical depth (TOD) for visible range. Based on our measurements, it is found that the seasonal and sky conditional percentages of the global PAR for the direct and diffuse components depend considerably on the magnitude of the TOD. Annual mean diffuse PAR at Seoul appears to be 51% of the global-horizontal PAR (5.12 ± 1.27 M J m-2 d-1) for all-sky conditions with a TOD of 1.02 ± 0.32. However, the diffuse PAR are 39% of the global PAR (6.10 ± 2.27 M J m-2 d-1) under clear-sky conditions (cloud amount ≤ 2/10) with a TOD of 0.47 ± 0.23 and 73% of the global PAR (2.99 ± 2.07 M J m-2 d-1) under cloudy sky conditions (cloud amount ≥ 8/10) with a TOD of 1.80 ± 0.45, respectively. Simple statistical models are presented for the determination of direct and diffuse-horizontal PAR as a function of TOD, which is fitted by a curvilinear regression at a given solar zenith angle (SZA). Overall, there was reasonable agreement between predicted and measured values of two PAR components. On the basis of the statistical models for direct and diffuse PAR, we found that the four parameters of the maximum diffuse PAR, the TOD corresponding to the maximum diffuse PAR, the PAR and TOD when direct and diffuse PAR have the same value, decrease all with increasing SZA. It is of interest to note that these all four parameters can be expressed as simple linear functions of SZA.

Original languageEnglish
JournalJournal of Geophysical Research D: Atmospheres
Volume108
Issue number9
Publication statusPublished - 2003 May 16

Fingerprint

photosynthetically active radiation
irradiance
optical thickness
optical depth
solar radiation
Radiometers
sky
zenith
statistical models
zenith angle
radiometers
Statistical Models
regression analysis
clear sky
radiometer

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

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title = "Dependence of diffuse photosynthetically active solar irradiance on total optical depth",
abstract = "Photosynthetically active solar irradiance (PAR, 400-700 nm) data measured with a rotating shadowband radiometer at Yonsei University, Seoul (37.57°N, 126.97°E) from 1996 through 1997 have been analyzed to investigate statistical features in components of the horizontal PAR and the dependence of the diffuse PAR on total optical depth (TOD) for visible range. Based on our measurements, it is found that the seasonal and sky conditional percentages of the global PAR for the direct and diffuse components depend considerably on the magnitude of the TOD. Annual mean diffuse PAR at Seoul appears to be 51{\%} of the global-horizontal PAR (5.12 ± 1.27 M J m-2 d-1) for all-sky conditions with a TOD of 1.02 ± 0.32. However, the diffuse PAR are 39{\%} of the global PAR (6.10 ± 2.27 M J m-2 d-1) under clear-sky conditions (cloud amount ≤ 2/10) with a TOD of 0.47 ± 0.23 and 73{\%} of the global PAR (2.99 ± 2.07 M J m-2 d-1) under cloudy sky conditions (cloud amount ≥ 8/10) with a TOD of 1.80 ± 0.45, respectively. Simple statistical models are presented for the determination of direct and diffuse-horizontal PAR as a function of TOD, which is fitted by a curvilinear regression at a given solar zenith angle (SZA). Overall, there was reasonable agreement between predicted and measured values of two PAR components. On the basis of the statistical models for direct and diffuse PAR, we found that the four parameters of the maximum diffuse PAR, the TOD corresponding to the maximum diffuse PAR, the PAR and TOD when direct and diffuse PAR have the same value, decrease all with increasing SZA. It is of interest to note that these all four parameters can be expressed as simple linear functions of SZA.",
author = "Cho, {Hi Ku} and Jeong, {Myeong J.} and Jhoon Kim and Kim, {Young J.}",
year = "2003",
month = "5",
day = "16",
language = "English",
volume = "108",
journal = "Journal of Geophysical Research",
issn = "0148-0227",
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Dependence of diffuse photosynthetically active solar irradiance on total optical depth. / Cho, Hi Ku; Jeong, Myeong J.; Kim, Jhoon; Kim, Young J.

In: Journal of Geophysical Research D: Atmospheres, Vol. 108, No. 9, 16.05.2003.

Research output: Contribution to journalArticle

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T1 - Dependence of diffuse photosynthetically active solar irradiance on total optical depth

AU - Cho, Hi Ku

AU - Jeong, Myeong J.

AU - Kim, Jhoon

AU - Kim, Young J.

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N2 - Photosynthetically active solar irradiance (PAR, 400-700 nm) data measured with a rotating shadowband radiometer at Yonsei University, Seoul (37.57°N, 126.97°E) from 1996 through 1997 have been analyzed to investigate statistical features in components of the horizontal PAR and the dependence of the diffuse PAR on total optical depth (TOD) for visible range. Based on our measurements, it is found that the seasonal and sky conditional percentages of the global PAR for the direct and diffuse components depend considerably on the magnitude of the TOD. Annual mean diffuse PAR at Seoul appears to be 51% of the global-horizontal PAR (5.12 ± 1.27 M J m-2 d-1) for all-sky conditions with a TOD of 1.02 ± 0.32. However, the diffuse PAR are 39% of the global PAR (6.10 ± 2.27 M J m-2 d-1) under clear-sky conditions (cloud amount ≤ 2/10) with a TOD of 0.47 ± 0.23 and 73% of the global PAR (2.99 ± 2.07 M J m-2 d-1) under cloudy sky conditions (cloud amount ≥ 8/10) with a TOD of 1.80 ± 0.45, respectively. Simple statistical models are presented for the determination of direct and diffuse-horizontal PAR as a function of TOD, which is fitted by a curvilinear regression at a given solar zenith angle (SZA). Overall, there was reasonable agreement between predicted and measured values of two PAR components. On the basis of the statistical models for direct and diffuse PAR, we found that the four parameters of the maximum diffuse PAR, the TOD corresponding to the maximum diffuse PAR, the PAR and TOD when direct and diffuse PAR have the same value, decrease all with increasing SZA. It is of interest to note that these all four parameters can be expressed as simple linear functions of SZA.

AB - Photosynthetically active solar irradiance (PAR, 400-700 nm) data measured with a rotating shadowband radiometer at Yonsei University, Seoul (37.57°N, 126.97°E) from 1996 through 1997 have been analyzed to investigate statistical features in components of the horizontal PAR and the dependence of the diffuse PAR on total optical depth (TOD) for visible range. Based on our measurements, it is found that the seasonal and sky conditional percentages of the global PAR for the direct and diffuse components depend considerably on the magnitude of the TOD. Annual mean diffuse PAR at Seoul appears to be 51% of the global-horizontal PAR (5.12 ± 1.27 M J m-2 d-1) for all-sky conditions with a TOD of 1.02 ± 0.32. However, the diffuse PAR are 39% of the global PAR (6.10 ± 2.27 M J m-2 d-1) under clear-sky conditions (cloud amount ≤ 2/10) with a TOD of 0.47 ± 0.23 and 73% of the global PAR (2.99 ± 2.07 M J m-2 d-1) under cloudy sky conditions (cloud amount ≥ 8/10) with a TOD of 1.80 ± 0.45, respectively. Simple statistical models are presented for the determination of direct and diffuse-horizontal PAR as a function of TOD, which is fitted by a curvilinear regression at a given solar zenith angle (SZA). Overall, there was reasonable agreement between predicted and measured values of two PAR components. On the basis of the statistical models for direct and diffuse PAR, we found that the four parameters of the maximum diffuse PAR, the TOD corresponding to the maximum diffuse PAR, the PAR and TOD when direct and diffuse PAR have the same value, decrease all with increasing SZA. It is of interest to note that these all four parameters can be expressed as simple linear functions of SZA.

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